LDS scripture teaches that the words of an elder when moved by the Holy Ghost are to be considered scripture:

And whatsoever they shall speak when moved upon by the Holy Ghost shall be scripture, shall be the will of the Lord, shall be the mind of the Lord, shall be the word of the Lord, shall be the voice of the Lord, and the power of God unto salvation.
— Doctrine and Covenants 68:4

Brigham Young, the second and longest serving Mormon prophet, said that all of his sermons are to be considered scripture:

I have never yet preached a sermon and sent it out to the children of men, that they may not call Scripture.